I think there are a number of behaviors outside the dojo which if I knew about would cause me to ask the person not to train - for the group and my own piece of mind. I'll leave that to your imagination.

I'll even step out on the limb here and make a generalization. The very people who demand a teacher take all comers are often very quick to demand a higher moral standard from the instructor (in fact the demand is implicit and ironic). The harmony that we talk about is not one way.